Method for preparing organohalogenosilanes



Patented May 27, 1952 METHOD FOR PREPARING ORGANOHALO- GENOSILANES Donald Mohler, Schenectady, and Jesse E. Sellers, Scotia, N. Y., assignors to General Electric Company, a corporation of New York No Drawing. Application September 21, 1949, Serial No. 117,074

4 Claims. 1

This invention relate to the preparation of organohalogenosilanes. More particularly, it is concerned with a process for preparing organehalogenosilanes which comprises effecting reaction between (1) an aromatic (e. g., aryl) halide and (2) a halogenosilane containing a siliconbonded hydrogen atom and a silicon-bonded halogen atom, thereby to form an aromatic halogenosilane containing less halogen in the aromatic nucleus than was originally present in the aromatic nucleus of the aromatic halide.

It has been disclosed in U. S. patent 2,379,821, issued July 3, 1945, that organohalogenosilanes may be prepared by efiecting reaction between a hydrocarbon and an inorganic silicon halide in the vapor phase at a temperature of at least 450 C. The patentees disclose that the hydrocarbons may contain a substituent thereon, specifically a halogen. Referring to such a halogen-substituted hydrocarbon, the patentees further point out that the halogen substituent is inert in'the reaction.

We have now discovered that, contrary to the disclosures and teachings in the aforementioned U. S. Patent 2,379,821, the presence of the halogen substituent on the aromatic hydrocarbon nucleus increases the reactivity of the aromatic hydrocarbon to such a degree that greatly improved yields of arylhalogenosilanes can be realized in the reaction between the halogen-substituted aromatic hydrocarbon and the aforementioned halogenosilane containing a silicon-bonded hydrogen atom and a silicon-bonded halogen atom. Moreover, we have found that, in addition to increasing the reactivity of the aryl hydrocarbon with the attendant result of being able to use much lower temperatures than is possible with hydrocarbon free of halogen substituents, the halogen substituent on the aryl hydrocarbon is so reactive as to be removed from the hydrocarbon residue, leaving behind an unsatisfied carbon valence which attaches to an unsatisfied silicon valence of the halogenosilane left vacant by the removal of a silicon-bonded hydrogen atom from the halogenosilane. As a result of our claimed reaction, which is identified by the following exemplary equation:

one of the by-products formed is a hydrogen halide whereas, according to the teachings and disclosures of the aforementioned U. S. Patent 2,379,821, one of the by-products formed is a molecule of hydrogen derived from an atom of hydrogen from the organic hydrocarbon and an atom of hydrogen from the halogenosilane, the halogen on the organic hydrocarbon remaining essentially inert and nonreactive in the reaction, according to the patentees.

In accordance with our invention, an aryl halide is reacted with a halogenosilane (for brevity herev action, higher or lower temperatures may be employed without departing from the scope of the invention and that we do not intend to be limited to the specific temperature ranges disclosed above. However, temperatures much above 600 C. usually result in undesirable excesses of complex materials due to decomposition, sid reactions, etc.

The aromatic halide employed in the practice of our invention may be generally stated to conform to the general formula RX where X is a halogen (e. g., chlorine, bromine, fluorine, etc.) and R is a monovalent aryl radical, such as, for instance, phenyl, naphthyl, anthracyl, tolyl, xylyl, ethylphenyl, etc. B, may also be a heterocyclic organic radical as, for instance, the furyl radical, the triazinyl radical, thienyl radical, etc.

It has been found that an aromatic hydrocarbon halide can be controlled better in our claimed invention than alkyl halides such as, for instance, methyl chloride which when reacted with SiHCls at 500 C. was found to explode. It will, of course; be understood that the aryl halide may also contain other substituents thereon as, for example, additional halogens, etc. Thus, we may employ additionally halogenated aromatic hydrocarbons as, for instance, dichlorobenzene, tribromobenzene, tetrachlorobenzene, hexachlorobenzene, etc.

As pointed out previously, the aromatic halide is caused to react with a halogenosilane containing a silicon-bonded hydrogen atom and a siliconbonded halogen atom. Examples of such halogenosilanes are, for instance, SlI-ICls, SiHzClz, SiHaCl, SlI-IBIs, CHsSiI-IClz, (CI-I3)2SiI-ICl, C6H5SiHBl2, (C6I'1'sCH2)2SiHC1, CH3CsH4SiHC12, (C2H5)SiH2C1, CsHnSiHClz, etc. Generally, the halogenosilanes employed in the practice of this invention will conform to the formula where A is a halogen (for instance, chlorine,

bromine, etc.), R is, for instance, a monovalent equal to from 1 to 3, inclusive, the total of m and n being equal to at most 4.

In practicing our invention, the aromatic halide and halogenosilane are preferably passed together through a heated reaction zone maintained at a suitable temperature. Thus, we'have found it advantageousto pass the mixture of reactants through a heated 'tube'maintained at the desired temperature depending upon the reactants used, the time of contact, etc. Such vapor phase operations are preferable since they lend themselves readily to continuous processing while at the same time permitting the use of higher temperatures because the time of contact at these elevated temperatures is much less than in the case of batch operations. We have found it desirable, where the reactants are being passed through a heated reaction zone, to employ inert materials in the zone to aid in the uniform heating of the vapors or gases. Among such compositions may be mentioned carborundum, heat-resistant glass beads, -silica, porcelain, carbon, etc., as well as othermaterials resistant to and nonreactive with tliereactants or the reaction product.

nearer course, be apparent to those skilled in them ftha'tbtl'i'er methods may "be employed for'eift-ing the -reaction without departing from the scope of our claimed invention. Thus, one mayheat the reactants in a closed reaction vessel under piessurersra period of time sufiicient to cause aiereadu nto go to completion.

The fatio of'the aromatic halide to the halognosil-a'ne may be varied within wide limits. Geiiefallmfthes'ereactants are preferably present in amateur 055 to -3 or more mols of the aromatic halide per mol of the halogenosilane.

However, as will be apparent to those skilled in the artfexces's molar amounts of either the haloge'nosil'ane brine organiehalide may also be employed. We have found it advisable for economicalpurposesand for the purpose of effecting a 'mdre boin-plte reaction'between the reactants tou's'eamolarex'cess of the aromatic halide, for instah'c'effroin l to 2'mols of the aromatic halide per mol offthe --halogenosila'ne.

Generally throughout the reaction between the aromatic halide 3 shame halogenosilane, caution should -'betal n'to maintain substantially anhydrous conditions in "order to minimize undesirable hydrolysis 'jof either the halogenosilane or the formed orgariohalo'genos'ilanes. In addition, we have f'odri'dfit "advantageous to employ vapor phase 'operaudus when using aromatic halides, for example, 'chlorobenzene, as one of the reacta'nts, 'with the 'halo'genosilane. Such vapor phase procedures permit easier escape of hydrogen muqe'wmcn u maintained for too long a time' incontaiitwith any formed aromatic halogendsilahs, "for instance, phenyltrichlorosilane. teud's'to' reduce "the yields of the latter due to fission of the carbon-silicon bond by the hydrogen halide. I In this'r'e'spect, the vapor phase reaction isalmost anecessity in order to obtain satisfactoryyields. p

In orderthat those skilled in the art may better understandhow the present invention may be practicedfthefollowing examples are given by Way of illustration and not by way of limitation. All parts are by'weight.

An iron tube was packed with silica gel beads, and a mixture of inonochlorobenzene and trichlorosilane waspassed through the heated tube at various temperatures,v pressures and rates. Another reaction tube was packed with pieces of porcelain scrap, while in'another case (sample No. 7) no packing was employed in the reaction tube. In one sample test (sample No. 10) benzene was substituted iniplace of the chlorobenzene used in the other runs. In each case the I former to one mol of the latter.

Table No. I

"r 'P Rate d 3*? P 1;

8m" H- C OIO" 1 3.1165 80 mg Q peratnre sure 23 Per Part [711- In Reactor C. p. s. i. Hour recovered Tri- Tube chlorosilanc L520 0 115 0.351 Head's .470 it 115 0. 315 'Do. 520 40 300' 0. 425 "D0. 575 1.6? 0:269 iDO. 520 50. 107: 0. 369. ,Do. '570 '103' O. 446 'Do.

520 01 1171 .0.:578= None. .520 0 .122: 0. 240 Porcelain. 520 -0 0. 337 1130. 535 0 V 115' 0.000, B65118.

A mixture of orthodichlorob'enzene and trichlorosilanelSil-ICla) was passed through {to a heated tube maintained at-a temperatureof about 525 C. while-permitting theHCIjto escape-as fast as it formed, Thereaction product comprised "a mixture of chlorophenylchlorosilanes, includin chlorophenyltrichlorosilane.

earners-*3 Trichlorobenaene, htriohlorosilane "were passed throughga jheated tube-maintained :at a

temperature of about 5-25;C. "using conditions similar to those as-inExample The reaction product contained a large amountofhigh boiling chlorosilanes, including a mixture of dichlorophenylchlorosilanes.

Chlorotoluene and trichlorosilane werepassed together through aheated tube maintained at a temperature, of aboiltj525 C, The; 10w;b0i1ing materials, including chlorotoluene and trichlorosilane, were removed: from the reaction -product and the remaining mixture which had aboiling point range for tolyltrichlorosilane was hydrolyzed by pouring-in water to yield a resinous product.

' mixture of 1,2514 trichlorobenzeneand' mothyldichlorosilan'e (QHgSiHClz') fin the molar ratio of 1.25 'mols of the rorm-er ,per 'mol ofthe latter was passed 'througha hot "tubefathtmosspheric pressure maintained at a temperature (if about 500 'c The" mixture or reactantsiwas out through the'heate'd'irontu'be at'a'rate of about 500 parts per hour. Fractional distillationo f' the reaction pmduct yielded about lsojparts of a fraction boiling between and C. at 29 mm. This material, 'whenanalyz'edjslidwed contain 27 .1 per 'cent'hydrolyaable' 'ch'lor e, had a density at 26 Cjo'f 111410. The value for hydroly'z'able chlorine {if phenylmethyldichlorosilane is "27 $3 per; ce

Anothe'r' run was conducted at 600? 'C.

a somewhat lower yieldof aprtauct boiliiig between 156 "an'd 16'6 C. at mars? action had a'hydrolyzable"'chloriiie'fialiie of 910 per cent, a density at '26"C. oif 12410, are "as also believed to be'"dichlorophenyliifthyldichlorosila'ile.

EXAMPLE 6 EXAMPLE '7 1,2,4-trichlorobenzene and trichlorosilane in the molar ratio of 1.25 mols of the former to 1 mol of the latter were passed at atmospheric pressure through a hot tube maintained at 500 C. Fractional distillation and analysis of the reaction product showed that substantial amounts of dichlorophenyltrichlorosilane had been formed. Thus, it was found that about 120 parts of the latter compound were obtained boiling between 165 and 175 C. at 29 mm. from about 700 parts of the mixture of reactants.

When the above conditions and proportions of reactants were repeated with the exception that the temperature of reaction was 600 C. and the rate of through-put was about 500 to 525 parts per hour, there was obtained about 225 parts of a fraction boiling between 150 and 170 C. at 29 mm. which analysis showed to be almost pure dichlorophenyltrichlorosilane.

The two fractions from the 500 C. and 600 C. runs were combined and redistilled to obtain essentially pure dichlorophenyltrichlorosilane boiling at 155 C. at 27 mm. and having a density at 26 C. of 1.537. Analysis of this compound showed it to have an average value of 37.6 per cent hydrolyzable chlorine which compared favorably with the theoretical value of 38.0 per cent.

EXAMPLE 8 Orthodichlorobenzene and trichlorosilane in the molar ratio of 1.25 mols of the former per mol of the latter were passed through an iron tube at atmospheric pressure at a temperature of about 500 C. In all, two runs were made on this mixture using a total of about 950 parts of feed, one run using a rate of about 525 parts of the mixture of reactants per hour and the other 500 parts of the mixture of the reactants per hour. In the first run, approximately 140 parts of a product boiling between 150 and 153 C. at 47 mm. were obtained. Analysis of this sample showed it to have a density at 26 C. of 1.443 and 42.0 per cent hydrolyzable chlorine. Distillation of the second run yielded about 115 parts of a fraction boiling between 132 and 140 C. at 30 mm. and having a density at 26 C. of 1.448 and 43.8 per cent hydrolyzable chlorine value. It appeared that good yields of chlorophenyltrichlorosilane were obtained as evidenced by the fact that the theoretical hydrolyzable chlorine value for this compound is 43.3 per cent.

EXAMPLE 9 In this experiment, a mixture of 230 parts methyldichlorosilane and 553 parts chlorobenzene was passed through a hot tube, without packing or catalysts, maintained at a temperature of 550 C. at atmospheric pressure. Fractional distillation and analysis of the reaction product indicated sizable proportions of methyl- 6f phenyldichlorosilane were obtained in the reaction.

EXAMPLE 10 A mixture of ingredients comprising approximately in the molar ratio of 2 mols 2-chlorothiophene (thienyl chloride) and 1 mol trichlorosilane was passed through a hot iron tube at atmospheric pressure and maintained at a temperature of 525 C. Approximately one-third of the reaction product having a boiling point of 108 C. at 45 mm.was isolated by fractional distillation. This product on analysis was shown to have a value of 48.7 per cent hydrolyzable chlorine. The theoretical value for hydrolyzable chlorine for thienyl trichlorosilane is 49.0 per cent, establishing that the bulk of the reaction product was, in fact, this compound. The density of the compound was found to be 1.427 at 26 C.

Hydrolysis of the thienyl trichlorosilane in a hydrolyzing medium comprising water and ethyl ether resulted in separation of an ether layer which when removed from the water layer and the ether removed by heating, left behind a resin which was hard, brittle and nearly water-white in color. The resin was obtained essentially in a quantitative yield. Heating of this resin showed that its heat stability compared favorably with the heat stability of resins made from phenyl trichlorosilane and that the sulfur in the thienyl nucleus was stable.

EXAMPLE 1 1 2 chlorothiophene (thienyl chloride) and methyl dichlorosilane (CHsSiI-IClz) in a molar ratio of 2:1 were passed through a hot iron tube maintained under the same conditions as in Example 10. Fractional distillation of the reaction product yielded a fraction approximately oneseventh the weight of the total reaction product boiling at 101 C. at 34 mm. which on analysis was shown to have a value of 35.3 per cent hydrolyzable chlorine. The theoretical value of thienyl methyl dichlorosilane HG OH C1 (Hi than.) S JHa is 36.0 per cent hydrolyzable chlorine thus establishing the formation of the latter compound. The density of this composition at 28 C. was found to be 1.313.

In all the foregoing examples, in addition to the desired reaction product, there are also present varying amounts of unreacted halogenosilanes and aromatic halides, together with byproducts of the reaction including silicon tetrachloride. The unreacted materials can be recycled or reused again in future reactions.

Although temperatures within the range from about 470C. to 600 C. have been disclosed as having been used in the foregoing examples, it will be apparent that higher or lower temperatures may be employed without departing from the scope of the invention. The upper limit of the temperature range is generally determined by the stability of the reactants under the reaction conditions as well as the reaction product. Usually, this upper limit is one below which unsmegma:

desirable decomposition: offieither-the-reactants or the reaction product takes place.

In addition to the -reactions; described in the foregoing examples, it willbe apparent that other combinations of reactants, arciincluded within. the scope of ourfclaimedftinyention. Thus,- one may 7 eifect reaction between, for instance, difchlorosilane (SiHiCl'i) and ichlorobenzene to pro-, duce such materials asbfor example, ,phenyldichlorosilane (CeHs'SiI-IClzl andjdiphenyldichlorosilane. [(CsH)'2S iClz]; of our inyentionthe reaction between thehal'ogenosilane and the aromatic halide resultsin the formation oi a moleculjeofihydrogemhalide the atoms of the hydrogen halide be ngpderived from the hydrogen of the halogenosilane and the halogen of the aromatic halide.

We have also discovered that 1W8 are able to obtain improved yields of aromatic halogenasilanes by effecting the reaction between the aromatic halide V and the -halogenosilane containing; at least one silicon-bonded hydro en-and 812118351)" one silicon-bonded halogenin the presence of metallic palladium. The palladium may bemsed' in several ways; One method comprisesdepositing the palladium in the formlof adilute aqueous palladium nitratesolutionon an; inert inorganic packing as, for example, glasswoolr .The follow:-

ing example illustrates the :advantages-.-obtained using palladium-asa catalyst :ior the reaction between chlorobenzeneqand ,SiHCl3.--

EXAMPLE 12' In: the followingqruns a mixture of chlorobenzene and SiI-ICls the molar ratio. of :twoparts of the former per part ofgthe lattenwas passed at a temperature of about 525 C. through each of four steel tubes a-bout54" long and 2 diameter.) for equal lengths ,of, time using essentiallyrthe same amountaof reactantsand. employing, thesame rate-of passagewof, the mixture.

In run:.No.,1 novpacking andno catalyst wereemployed, the mixtureoi reactantsbeing merely passed throughtatthe stipulated temperature of 525 C. In run Not 2.the tube-waspacked with glasssawool thoroughly saturated-L with a. dilute aqueous, palladium nitrate, solution. Thatube withits treatedglass wool packing was heatedat a temperature of about\5.00 to 600- C. for approximately eight hours to drive off the Water and to decompose the palladium nitrate to metallic palladium (aboutvl'i. grams) which was homogeneously dispersed throughout thepacking. The following table shows the results of the foregoing two runs:

Table No. 'II

Tempe" YieldPer Cent; 1 Run No. aggro Cams-Lela I Catalyst 1; 5251 f, 4 34.0 None; 2 525 41:8 Palladmmi From the foregoingi it t wilLbe apparent: that,

using palladium as. a-catalyst; .A approximately 20 per cent greater-yields ofr phenyltrichloro- Usually, in the practice silane can be realized sinuthemreactioni between.

chlorobenzene and. SiHCla. 'thaniis possible when. the palladiumris omitted. The ,amount-tof'epal-y ladium can be, varied within Wide limits; asowi-ll.

be apparent to: .those skilledin uthe art.

The organohalogenosilanes;obtainedjirriaccord ance-rwitlr our. claimedl process imam-be employedz 8 to render water-repellent surfaces originally waterrnon-repellent. In addition,- they may be used asintermediates in the preparation oforgano-v polysiloxane resins, oils, rubbersretc; .1

What we claim as new" and-desire tosecure by Letters Patent of the United States is:

1. The process-which comprisesipassing under substantially anhydrous conditions andin the vapor phase'a mixtureof-ingredients comprising. (1) chlorobenzene and=(2) methyldichlorosilanel throughla heated zone-maintainedat a tempera ture of around 450 to 575 O. and containingiaa catalyst comprisingpalladium, thereby to obtain methyl phenyldichlorosilana'and thereafter isolating :the. aforesaid methyl phenyldichlorosilane.

2; Thexfprocess. which: comprises :passingzunder.

substantially anhydrous conditions-end in: the

vapor phase 2 a; mixture comprising (1): dichlorobenzene and; (2); trichlorosilane through? alihate ed zone=maintained at tantemperatureof around 450 "tor-575? C. and.containingra;catalystzicoms prising palladium, thereby: topotainchlorophe nyltrichlorosilane, and thereafter: isolating'ithe" aforementioned chiorophenyltrichlorosilane.

3. The process. which: comprisesipassingmnder substantially anhydrous conditions and in "the.

vapor phase amixture comprising (1) anaromatic halide. in which the. only substituentlon" the aromatic nucleus is halogenuivhich isxattache'd directlyto the saidlaromatic nucleus and 12) a halogenosilane corresponding to; the general for' mule; SiHmXtEr-m-n, where X islhalogemRiis-au monovalent. hydrocarbon radical; and f m and i n are each integers equal to fr'om 1 to :3 inclusive, the totalof m andm being equal to at most 4,

the said passage of ingredients being conducted through a heated zonecontainingacatalyst comprising palladium and maintained--ata'temperature of around 450 575""C., thereby to obtain an aromatic halogenosilane containing the arcmatic group attached to silicon by a carbon-silhcon linkage and therebeing present in-the varornatic nucleus one less-halogen than was originally attached thereto, and'thereafter isolating the aforesaid aromatic halogenosilane.

1-. 5 The process which comprises massing-under" substantially anhydrous conditions and "in-the vapor phase'a mixture comprising (1 chlorobenzene-and (2) trichlorosilane-through a heat ed zone containing a catalyst com-prising pallet-- dium and maintained at-a temperature of around 459 to 575 0., thereby to obtain phenyltrichlorosilane,- and thereafter '-isolatingthe I aforesaid phenyltrichlorosilane.- v

- DONALD MOHLER? JESSE E. SELLERS:

REFERENCES" CITED The following references: are' of: record in the 

1. THE PROCESS WHICH COMPRISES PASSING UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AND IN THE VAPOR PHASES A MIXTURE OF INGREDIENTS COMPRISING (1) CHLOROBENZENE AND (2) METHYLDICHLOROSILANE THROUGH A HEATED ZONE MAINTAINED AT A TEMPERATURE OF AROUND 450* TO 575* C. AND CONTAINING A CATALYST COMPRISING PALLADIUM, THEREBY TO OBTAIN METHYL PHENYLDICHLOROSILANE, AND THEREAFTER ISOLATING THE AFORESAID METHYL PHENYLDICHLOROSILANE. 